Structural similarities among eight benzoylhydrazones

Abstract

The crystal structures of eight benzoylhydrazones with different substituents have been investigated, namely 1-benzoyl-2-(propan-2-ylidene)hydrazone, C10H12N2O, (I), 1-benzoyl-2-(1-cyclohexylethylidene)hydrazone, C15H20N2O, (II), 1-benzoyl-2-[1-(naphthalen-2-yl)ethylidene]hydrazone, C19H16N2O, (III), 1-benzoyl-2-(1-cyclohexylbenzylidene)hydrazone, C20H22N2O, (IV), 1-benzoyl-2-(1-phenylbenzylidene)hydrazone, C20H16N2O, (V), 1-benzoyl-2-[1-(4-chlorophenyl)benzylidene]hydrazone, C20H15ClN2O, (VI), 1-benzoyl-2-(4-hydroxybenzylidene)hydrazone methanol monosolvate, C14H12N2O2·CH3OH, (VII), and 1-benzoyl-2-(1,1-diphenylpropan-2-ylidene)hydrazone, C22H20N2O, (VIII). The ten molecules in the eight crystal structures [there are two independent molecules in the structures of (V) and (VI)] show similar conformations and hydrogen-bonding patterns. The C=N—NH—C=O group is planar, but the plane of the phenyl ring of the benzoyl group is rotated by about 30° with respect to that of the keto group [except for (IV), where the groups are coplanar]. Only in the amide group of (VIII) is the N—H groupsynto the C=O bond, whereas the seven other compounds exhibit theanticonformation. Unless prevented by steric hindrance, N—H...O hydrogen bonds help to stabilize the crystal structure, which leads to infinite chains or dimers depending upon the molecular conformation. The molecular packing is supported by intermolecular C—H...O interactions. In the crystal structure of (VII), the methanol solvent molecule participates in two strong hydrogen bonds and two weak C—H...O interactions, thus acting as a link between the molecular chains.